[PhilD]

Yeah, like Ming says: just build enough Snipers that anything that tries to cross the river dies quickly. Camp high-influence units on gold mines, and the AI will simply waste its resources on pointless attacks while you build up a large force of tanks. Then charge in.

Hint: a Tank with a Smith in range can kill a Vampire in one hit. Don't do this to too many tanks, though, as they need speed for the attack.